The size of giant fish in the Mekong River is shrinking at an alarming rate, with potentially devastating consequences for the region’s ecosystem and the millions who rely on the river for their livelihoods. A recent study found that the length of the largest freshwater giants, some of which can grow to the size of grizzly bears, has decreased by as much as 40% in just seven years.
Certain species, like the Mekong giant catfish, have been studied for longer periods and show an even more dramatic decline, with their weight decreasing by 55% over the last 25 years. Their average size has fallen from 180 kg to 80 kg.
Biologist Ngor Peng Bun recalled helping to catch a 270 kg Mekong giant catfish in 2000, before tagging and releasing it back into the river. “The size was very big, unforgettable,” he said, adding that the fish nearly capsized his boat.
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Known locally in Khmer as trey reach, or the “royal fish,” this species is now a shadow of its former self.
The giant barb, the world’s largest carp and too Cambodia’s national fish, is facing a similar fate. Both species are now listed as critically endangered, according to reporting from detikINET.
Size is crucial for survival, as larger fish produce significantly more eggs. A 300 kg catfish can generate 10 to 20 times more offspring than a 50 kg fish. Many of the largest species are also long-lived and slow to mature, meaning increased mortality rates can trigger population collapses.
Mekong giants are vital to the river’s ecosystem, but also central to the livelihoods of millions who depend on its fisheries. Scientists found a glimmer of hope in 2022 when a fisherman caught and released a 300 kg stingray, breaking records as the largest freshwater fish ever discovered, suggesting some giants still remain.
The practice of targeting and hunting the largest animals often leads to the decline of many species, including Atlantic cod in the Baltic Sea, Alaskan salmon, and even smaller tusk sizes in African elephants. Dr. Zeb Hogan, a professor at the University of Nevada, said the rapid decline of Mekong giants is particularly concerning.
“We’re seeing this pattern in the Atlantic cod fisheries, where decades of size-selective fishing removed the largest and most fertile fish, resulting in a dramatic collapse,” Hogan explained. “As size and reproductive capacity decline, Mekong fish are at risk of entering a ‘spiral of death.’ Populations persist but are no longer able to reproduce effectively.”
“Knowing these giants are shrinking, both in size and number, feels like losing a piece of Cambodia,” said Sophorn Uy from the Royal University of Agriculture in Phnom Penh. “Their existence has deep cultural and ecological significance.”
Hogan believes this trend of decline is likely to continue. In addition to overfishing, Mekong giants are struggling with dams that block migration routes, the climate crisis, and deforestation for agriculture, which destroys crucial habitat.
The 300 kg stingray demonstrates that it’s not too late to act, but action is needed now to protect these species and their river system. “The future of Mekong giants is on the brink,” Hogan warned. Catching giant fish is already illegal in some countries along the Mekong River, but enforcement remains a significant challenge.
(fyk/fyk)
